352 PROFESSOR OWEN ON THE GENUS DINORNIS. 



orbit, occupying the anterior part of the interorbital space, joining each other at the 

 median line by an extensive vertical cellular surface, and dividing the orbital from the 

 rhinal cavities. In Apteryx and Dinornis the latter cavities are so developed as to 

 extend backward between the orbits to the cranium, the front wall of which forms the 

 back wall of the rhinal instead of the orbital cavities. 



The temporal fossa (Pis. LIII., LIV., LV. r) is divided by the pretympanic ridge and 

 process of the mastoi d 8") into a posterior compartment (PI. LV. fig. 1, s) for the pos- 

 terior ' temporalis ' muscle, of a triangular shape, 10 lines broad at the upper part, and 

 an anterior larger and deeper depression (ib. 7'), rounded above, 1 inch 5 lines in 

 breadth, and bounded anteriorly by the broad, triangular, vertically descending post- 

 frontal (ib. 12). These temporal fossfe, as in the less perfect skull (PI. LIII. fig. 1, 7'), 

 are nearly 2 inches apart on the broad, flattened upper surface of the cranium (7), 

 where the boundary-ridge is scarcely, if at all, defined. 



The orbit (PI. LV. o) is smaller in proportion to the size of the skull than in most 

 birds, but is much better defined than in the nocturnal Apteryx. The bony boundary 

 is formed posteriorly by the convex border of the postfrontal (12), above and in front 

 of this by the thin superorbital part of the frontal, which is gently wavy ; it then curves 

 down as a thicker triangular process (a) to form the fore part of the orbital frame. 

 The inner surface of this process developes a low vertical ridge, in part articulated with 

 the outer portion of the rhinal cincture ; and the lower part of this ridge is pierced by 

 the lacrymal foramen, indicating the process to be a lacrymal (ib. 73) confluent with the 

 frontal and prefrontal. 



The nasal is, in like manner, confluent by its upper border (PI. LIII. fig. 1, PI. LVI. 

 fig. 3, 15) with the frontal, its outer descending maxillary process (PI. LV. fig. 1, PI. LVI. 

 fig. 3, 15' ) terminating freely by a slight expansion which rests upon the maxillary 

 (PI. LV. fig. 1, 21). The premaxillary process of the nasal (is) is broad and flat, sup- 

 ported by the prefrontal expanse (PI. LVI. fig. 3, iv ) ; it is in great part excavated 

 above by the shallow rough depression for the premaxillary stem (PI. LIII. fig. 1, 22'), 

 and shows a narrow, thickened, and smooth tract bounding that depression externally 

 or laterally. 



The plane of the orbital cavity, so far as it is formed by bone, is directed from 

 behind obliquely forward and upward at an angle of 45° with the axis of the skull, the 

 eyes thus being directed more forward and downward than in birds generally. The 

 downward cast of the eyes relates to the great height of the Dinornw, and the 

 position of its food upon the ground. The roof of the orbit shows an oblong shallow 

 depression at its back part for the Harderian gland, and a deeper anterior pit for the 

 lacrymal gland. The fore part of the maxillary (PI. LVI. fig. 1, 21') is an oblong, bony, 

 pneumatic capsule, 2 inches in length and 1 inch 3 lines in breadth, flattened below, 

 where the surface is equally divided between the sutural part underlapped by the 

 maxillo-palatal part of the premaxillary ( 22" ) and the free, smooth surface, extending 



